Six-degree-of-freedom desktop interaction mechanical arm

Abstract

The six-degree-of-freedom desktop interaction mechanical arm comprises a base used for being fixedly installed on a working face, the base is a hollow box body, and an opening is formed in the top of the base; a first joint is installed in the base, the center point of the first joint coincides with the center point of the base, and an output shaft of the first joint is vertically upward. A second joint, a third joint, a fourth joint, a fifth joint and a sixth joint are sequentially connected to the first joint in series. Wherein the output shafts of the adjacent joints are parallel or perpendicular to each other; the position relation of the output shafts of the six joints is set, the D-H parameter set of the mechanical arm can be greatly reduced due to the fact that the output shafts of the adjacent joints are parallel or perpendicular to each other, and therefore the number of parameters established in a coordinate system of the mechanical arm is reduced, and the inverse kinematics solving speed is increased.

Description

Technical Field

[0001] This utility model belongs to the field of robotic arm technology, and in particular relates to a six-degree-of-freedom desktop interactive robotic arm. Background Technology

[0002] The six-degree-of-freedom desktop interactive robotic arm is a miniaturized and highly flexible robotic device that is widely used in education, scientific research, industrial automation, and human-robot collaboration.

[0003] Solving the inverse kinematics of a six-DOF robotic arm is more complex than that of a low-DOF robotic arm, requiring the inverse kinematics of each joint angle to be derived from the target position and orientation of the end effector. This high-dimensional inverse kinematics problem can lead to increased computational complexity, especially in real-time control scenarios, where computational latency can affect the robotic arm's response speed.

[0004] The inverse kinematics solution of a six-DOF manipulator depends on the establishment of coordinate system parameters. However, the traditional six-DOF manipulator has a large number of coordinate system parameters, which further limits the speed of its inverse kinematics solution. Utility Model Content

[0005] The purpose of this invention is to provide a six-degree-of-freedom desktop interactive robotic arm to reduce the number of coordinate system establishment parameters and improve the speed of inverse kinematics solution.

[0006] The present invention adopts the following technical solution: a six-degree-of-freedom desktop interactive robotic arm, including a base for fixed installation on a working surface, the base being a hollow box with an open top;

[0007] The first joint is installed inside the base, and the center point of the first joint coincides with the center point of the base. The output shaft of the first joint is vertically upward.

[0008] The first joint is connected in sequence with the second, third, fourth, fifth and sixth joints;

[0009] In this context, the output axes of adjacent joints are either parallel or perpendicular to each other.

[0010] Furthermore, the first joint and the second joint are fixedly connected by the first connecting arm;

[0011] The output shaft of the first joint is set perpendicular to the output shaft of the second joint;

[0012] The first connecting arm includes a first horizontal plate and a first vertical plate that are vertically connected. The first horizontal plate is fixedly mounted on the output shaft of the first joint, and one side of the vertical plate serves as a mounting seat for the second joint.

[0013] Furthermore, the second and third joints are fixedly connected by the second connecting arm;

[0014] The output shaft of the second joint is set parallel to the output shaft of the third joint;

[0015] The second connecting arm includes a second vertical plate and a third vertical plate arranged in parallel and staggered. The bottom end of the second vertical plate is fixedly installed on the output shaft of the second joint, and the top end of the third vertical plate serves as the mounting base for the third joint.

[0016] The second vertical plate and the third vertical plate are connected by a second horizontal plate, which is set perpendicular to the second vertical plate.

[0017] Furthermore, the third joint and the fourth joint are fixedly connected by the third connecting arm;

[0018] The output shaft of the third joint is set perpendicular to the output shaft of the fourth joint;

[0019] The third connecting arm includes a fourth vertical plate and a fifth vertical plate that are vertically connected. The fourth vertical plate is fixedly mounted on the output shaft of the third joint, and one side of the fifth vertical plate serves as a mounting base for the fourth joint.

[0020] Furthermore, the fourth joint and the fifth joint are fixedly connected by the fourth connecting arm;

[0021] The output shaft of the fourth joint is set perpendicular to the output shaft of the fifth joint;

[0022] The fourth connecting arm includes a sixth vertical plate and a seventh vertical plate that are vertically connected. The sixth vertical plate is fixedly mounted on the output shaft of the fourth joint, and one side of the seventh vertical plate serves as a mounting base for the fifth joint.

[0023] Furthermore, the fifth and sixth joints are fixedly connected by the fifth connecting arm;

[0024] The output shaft of the fifth joint is set perpendicularly to the output shaft of the sixth joint, and the output shaft of the sixth joint is coaxial with the output shaft of the fourth joint.

[0025] The fifth connecting arm includes an eighth vertical plate and a ninth vertical plate that are vertically connected. The eighth vertical plate is fixedly mounted on the output shaft of the fifth joint, and one side of the ninth vertical plate serves as a mounting base for the sixth joint.

[0026] Furthermore, the first connecting arm, the second connecting arm, the third connecting arm, the fourth connecting arm, and the fifth connecting arm are all provided with wire grooves.

[0027] Furthermore, a control box is connected to one side of the base, and there is a wire hole between the control box and the base. The control box is used to install the control board.

[0028] Furthermore, in the initial state, the installation heights of the first, second, third, and fourth joints increase sequentially.

[0029] The beneficial effects of this invention are: by setting the positional relationship of the output axes of the six joints, and by making the output axes of adjacent joints parallel or perpendicular to each other, the DH parameter set of the robotic arm can be greatly reduced, thereby reducing the number of parameters for establishing the coordinate system of the robotic arm and improving the speed of inverse kinematics solution. Attached Figure Description

[0030] Figure 1 This is a schematic diagram of the structure of a six-degree-of-freedom desktop interactive robotic arm according to an embodiment of the present invention;

[0031] Figure 2 This is a structural schematic diagram of a six-degree-of-freedom desktop interactive robotic arm from another perspective, according to an embodiment of the present invention.

[0032] Figure 3 This is a structural schematic diagram of a six-degree-of-freedom desktop interactive robotic arm from another perspective, representing an embodiment of this utility model.

[0033] Wherein: 10. First joint; 11. First connecting arm; 20. Second joint; 21. Second connecting arm; 30. Third joint; 31. Third connecting arm; 40. Fourth joint; 41. Fourth connecting arm; 50. Fifth joint; 51. Fifth connecting arm; 60. Sixth joint; 70. Control box. Detailed Implementation

[0034] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0035] With the surge in demand for laboratory automation and educational robots, robotic arms urgently need to overcome three major bottlenecks: bulkiness, high cost, and low interactivity. Traditional robotic arms suffer from size and cost drawbacks: they rely on a single harmonic / planetary reduction scheme, with high-precision harmonic reducers being expensive, while planetary reducers require additional backlash compensation design, increasing production costs by 30%-40%; discrete drive circuits and single-core MCU architectures require complex peripheral circuits, resulting in 40% redundancy in PCB area, further increasing hardware costs.

[0036] This utility model discloses a six-degree-of-freedom desktop interactive robotic arm, including a base for fixed installation on a work surface. The base is a hollow box with an open top. A first joint 10 is installed inside the base, and the center point of the first joint 10 coincides with the center point of the base. The output shaft of the first joint 10 is vertically upward. A second joint 20, a third joint 30, a fourth joint 40, a fifth joint 50, and a sixth joint 60 are connected in series on the first joint 10. The output shafts of adjacent joints are parallel or perpendicular to each other.

[0037] This invention sets the output axis position relationship of the six joints. By making the output axes of adjacent joints parallel or perpendicular to each other, the DH parameter set of the robot arm can be greatly reduced, thereby reducing the number of parameters for establishing the coordinate system of the robot arm and improving the speed of inverse kinematics solution.

[0038] The joints in this invention consist of a motor and a planetary reducer. Adjacent joints refer to two joints that are connected in series, such as the first joint 10 and the second joint 20, the second joint 20 and the third joint 30, the fifth joint 50 and the sixth joint 60, etc. The output shafts of adjacent joints being parallel or perpendicular to each other means that the axes of the output shafts of adjacent joints are parallel or perpendicular to each other.

[0039] In one embodiment, such as Figure 1 As shown, the first joint 10 and the second joint 20 are fixedly connected by a first connecting arm 11; the output shaft of the first joint 10 is perpendicular to the output shaft of the second joint 20; the first connecting arm 11 includes a first horizontal plate and a first vertical plate that are vertically connected, the first horizontal plate is fixedly mounted on the output shaft of the first joint 10, and one side of the vertical plate serves as a mounting seat for the second joint 20.

[0040] In this embodiment, the first connecting arm 11 is an L-shaped plate, and the first vertical plate is not set vertically, but is set vertically inclined. This ensures that the first joint 10 and the second joint 20 are staggered vertically, thereby increasing the movement space of part of the connecting arm.

[0041] Furthermore, such as Figure 2 As shown, the second joint 20 and the third joint 30 are fixedly connected by a second connecting arm 21; the output shaft of the second joint 20 is parallel to the output shaft of the third joint 30; the second connecting arm 21 includes a second vertical plate and a third vertical plate arranged in parallel and staggered arrangement, with the bottom end of the second vertical plate fixedly mounted on the output shaft of the second joint 20, and the top end of the third vertical plate serving as a mounting base for the third joint; the second vertical plate and the third vertical plate are connected by a second horizontal plate, which is perpendicular to the second vertical plate. Regarding the connection between the output shaft and the horizontal or vertical plate, threaded holes can be designed on the horizontal or vertical plate, and external threads can be provided on the output shaft, i.e., a threaded connection. Alternatively, it can be fixed by welding or other methods.

[0042] The second connecting arm 21, as the main moving arm in the robotic arm, is the longest among the connecting arms, so it is connected by two vertical plates. In addition, for the design of the joint position and the strength of the connecting arm, a second horizontal plate is added between the two vertical plates, and the length of the second horizontal plate is much smaller than that of the other two vertical plates.

[0043] In one embodiment, the third joint 30 and the fourth joint 40 are fixedly connected by a third connecting arm 31; the output shaft of the third joint 30 is perpendicular to the output shaft of the fourth joint 40; the third connecting arm 31 includes a fourth vertical plate and a fifth vertical plate that are vertically connected, the fourth vertical plate is fixedly mounted on the output shaft of the third joint 30, and one side of the fifth vertical plate serves as a mounting seat for the fourth joint 40. The design of the third connecting arm 31 ensures that the third joint 30 and the fourth joint 40 can rotate laterally.

[0044] In this embodiment of the invention, the fourth joint 40, the fifth joint 50, and the sixth joint 60 together constitute a spherical wrist joint. Specifically, as shown... Figure 3 As shown, the fourth joint 40 and the fifth joint 50 are fixedly connected by the fourth connecting arm 41; the output shaft of the fourth joint 40 is perpendicular to the output shaft of the fifth joint 50; the fourth connecting arm 41 includes a sixth vertical plate and a seventh vertical plate that are vertically connected, the sixth vertical plate is fixedly installed on the output shaft of the fourth joint 40, and one side of the seventh vertical plate serves as a mounting seat for the fifth joint 50.

[0045] The fifth joint 50 and the sixth joint 60 are fixedly connected by the fifth connecting arm 51. The output shaft of the fifth joint 50 is perpendicular to the output shaft of the sixth joint 60, and the output shaft of the sixth joint 60 is coaxial with the output shaft of the fourth joint 40. The fifth connecting arm 51 includes a vertically connected eighth vertical plate and a ninth vertical plate. The eighth vertical plate is fixedly mounted on the output shaft of the fifth joint 50, and one side of the ninth vertical plate serves as a mounting base for the sixth joint 60. The gripper can be installed at the end of the sixth joint 60 through a pre-drilled screw hole in the output shaft of the 3505 planetary reducer.

[0046] The first connecting arm 11, the second connecting arm 21, the third connecting arm 31, the fourth connecting arm 41, and the fifth connecting arm 51 are all provided with wire grooves. Moreover, these connecting arms adopt a honeycomb hollow design (such as a hollow ratio of 60%) to minimize the overall weight of the robotic arm.

[0047] In this utility model, a control box 70 is also connected to one side of the base. There is a wire hole between the control box 70 and the base. The control box 70 is used to install the control board, so that the robotic arm can be controlled as a whole through the control board.

[0048] In the initial state, the installation heights of the first joint 10, the second joint 20, the third joint 30, and the fourth joint 40 increase sequentially.

[0049] In this embodiment, a horizontal plate can be understood as a plate arranged horizontally, or a horizontally inclined plate with a certain angle of inclination relative to a horizontal plate; a vertical plate can be understood as a plate arranged vertically, or a vertical plate inclined at a certain angle relative to a vertical plate. Furthermore, to avoid confusion, the inclination angle of the horizontal plate (i.e., the angle between the horizontally inclined plate and the horizontal) is generally no greater than 15°, and similarly, the inclination angle of the vertical plate is generally no greater than 15°. As the most preferred embodiment, all horizontal plates in this invention are designed as horizontal plates, and all vertical plates are vertical plates perpendicular to the horizontal plate.

[0050] As a specific example, the joints mentioned above can be implemented using a motor and a planetary reducer. The connecting arm and the other skeleton components, such as the box, all use a T700 carbon fiber skeleton (5mm wall thickness) and a PLA-CF 3D printed shell with a honeycomb hollow design (60% hollowness). The electrical interface uses 24AWG high-temperature resistant soft silicone wire, an XT60 24V power supply socket, and an XH2.54-6P straight pin socket.

[0051] Furthermore, traditional current data is only used for current closed-loop control on the motor drive board. Building upon this, this invention scales the current sampling data (reducing it by a factor of 5) and transmits it to an external receiving module using CAN_FD communication, achieving force scaling feedback. In other words, in this embodiment, the connection between current sampling and external control is increased by adding a wiring path, thereby enabling force scaling feedback at the robotic arm's end effector.

[0052] In this embodiment, the coordinate system of the robotic arm in its initial state is analyzed. The coordinate system of the base and the coordinate system of the first joint coincide. Specifically, the origin of the base coordinate system is its center point, the x-axis points to the control box 70, the z-axis is vertically upward, and the y-axis direction can be determined according to the right-hand rule. Therefore, the coordinate system of the first joint 10 coincides with the ground coordinate system. In this way, the transformation matrix from the base to the first joint 10 can be eliminated, and the first joint 10 can be directly used as the world coordinate system. The computational load is reduced: one 4×4 matrix multiplication is eliminated (reducing 16 multiplication and addition operations); multiple joint rotation axes share a common point: each zero parameter reduces the number of non-zero elements in the matrix by two.

[0053] In the second joint coordinate system, the origin is the center point of the second joint 20, the z-axis is the axis of the output shaft of the second joint 20, and the direction is from the motor to the reducer (i.e. from the first vertical plate to the second vertical plate). The x-axis is parallel to the z-axis in the first joint coordinate system, and the y-axis is determined by the right-hand rule.

[0054] In the coordinate system of the third joint 30, the origin is the intersection point formed by projecting the output axis of the third joint 30 onto the output axis of the first joint 10. The z-axis of this coordinate system coincides with the output axis of the third joint 30, and its direction is from the fourth vertical plate to the third vertical plate. The x-axis is parallel to the z-axis in the coordinate system of the first joint and has the same direction. The y-axis is determined by the right-hand rule.

[0055] In the coordinate systems of the fourth joint 40, the fifth joint 50, and the sixth joint 60, the origin of the coordinates is located at the same point, which is the intersection of the output axis of the fifth joint 50 and the output axis of the fourth joint. Specifically, in the coordinate system of the fourth joint 40, the z-axis points from the fourth joint 40 towards the sixth joint 60, the x-axis points vertically upward, and the y-axis is determined using the right-hand rule. In the coordinate system of the fifth joint 50, the z-axis is the direction of the output axis of the fifth joint 50, pointing from the eighth vertical plate to the seventh vertical plate; the x-axis points vertically upward, and the y-axis is determined using the right-hand rule.

[0056] The x-axis and z-axis of the same axis but different coordinate systems are orthogonal, all adjacent joints are circumscribed on the z-axis, the proportion of quantitative elements in the matrix is ​​increased by 50%, and the number of multiplications is further reduced.

[0057] Through the structural design of the fourth joint 40, the fifth joint 50 and the sixth joint 60, their coordinate systems can be set to share the same origin, forming a spherical wrist structure. During inverse kinematics, it can be separated into position equations and attitude equations, further reducing the computational load by 60%.

[0058] Based on the determination of the coordinate system above, the DH parameters of the robotic arm in this embodiment are shown in Table 1.

[0059] Table 1

[0060] Joint number θ d a α First joint 0 0 0 0 Second joint π / 2 0 0 π / 2 Third joint 0 0 162mm 0 Fourth joint 0 71mm 0 π / 2 Fifth joint 0 0 0 π / 2 Sixth joint 0 0 0 π / 2

[0061] Where θ represents the joint angle, α represents the torsion angle, d represents the link offset, a represents the link length, 162mm refers to the length of the second connecting arm 21, and 71mm refers to the length of the sixth vertical plate.

[0062] As shown in Table 1, this invention, by constraining the mechanical structure of each joint and the corresponding connecting arm, makes multiple parameters constant at 0 or ±90°, which greatly simplifies the matrix elements and reduces the amount of calculation in the later stage.

[0063] In summary, the computational workload of a traditional six-DOF robotic arm is approximately 6 × 16 multiplications + 6 × 9 additions = 150 floating-point operations. However, this invention, after structural optimization, has 5 points where the link length is 0, 5 points where the link offset is 0, and 4 points where the torsion angle is 90° (π / 2 is in radians, converted to degrees is 90°). The simplified maximum computational workload per joint is 9 multiplications + 6 additions, for a total computational workload of 6 × 9 + 6 × 6 = 90 floating-point operations. It can be seen that 40% of the calculation steps are eliminated, significantly reducing the computational workload.

[0064] The control principle of the drive module of the robotic arm in this embodiment is as follows:

[0065] ① Motor speed command: The system first receives the target speed command of the motor and begins to execute the entire control process.

[0066] ② Speed ​​Loop PID: Based on the received speed command, the speed loop PID controller starts working. It compares the actual speed with the target speed, calculates the error, and adjusts the output SVPWM signal according to the PID algorithm to make the motor speed reach the target value.

[0067] ③ Q-axis target value = 0: In FOC motor control, the Q-axis (direct axis) is used to control the magnetic flux. Setting the target value of the Q-axis to 0 ensures that the motor operates under constant magnetic flux, achieving a stable current closed-loop control effect.

[0068] ④ D-axis PID and Q-axis PID: In FOC motor control, the D-axis PID controller is responsible for adjusting the motor torque, while the Q-axis PID controller is responsible for adjusting the magnetic flux. These two controllers work together to ensure that the motor achieves the desired torque and magnetic flux in the DQ coordinate system.

[0069] ⑤ Inverse Park Transformation and Inverse Clark Transformation: The current signal after being regulated by the PID controller needs to be transformed from the DQ coordinate system back to the three-phase stationary coordinate system through inverse Park transformation and inverse Clark transformation in order to generate a control signal suitable for the PMSM permanent magnet synchronous motor.

[0070] ⑥SVPWM Output: The generated space vector pulse width modulation (SVPWM) signal is used to control the PMSM permanent magnet synchronous motor, so that it runs at a predetermined speed and torque.

[0071] ⑦ Current sampling and Clark / Park transformation: When the motor is running, the current sampling module samples the motor's current value in real time. These current values ​​are transformed into current values ​​in a two-phase rotating coordinate system through two transformations, so that the PID controller can make adjustments.

[0072] ⑧ MT6701 magnetic encoder real-time angle reading: The system uses a 14-bit MT6701 magnetic encoder to read the motor's angle information in real time, and obtain the motor's actual operating electrical angle, angle, and speed information.

Claims

1. A six degree of freedom tabletop interactive robotic arm, characterized by, Includes a base for fixed installation on a work surface, the base being a hollow box with an open top; The base is equipped with a first joint (10), the center point of the first joint (10) coincides with the center point of the base, and the output shaft of the first joint (10) is vertically upward. The first joint (10) is connected in series with the second joint (20), the third joint (30), the fourth joint (40), the fifth joint (50) and the sixth joint (60). In this context, the output axes of adjacent joints are either parallel or perpendicular to each other.

2. The six degree-of-freedom desktop interactive robotic arm of claim 1, wherein, The first joint (10) and the second joint (20) are fixedly connected by a first connecting arm (11); The output shaft of the first joint (10) is perpendicular to the output shaft of the second joint (20); The first connecting arm (11) includes a first horizontal plate and a first vertical plate that are vertically connected. The first horizontal plate is fixedly mounted on the output shaft of the first joint (10), and one side of the vertical plate serves as a mounting seat for the second joint (20).

3. A six degree of freedom table-top interactive robotic arm as claimed in claim 2, wherein, The second joint (20) and the third joint (30) are fixedly connected by the second connecting arm (21); The output shaft of the second joint (20) is arranged parallel to the output shaft of the third joint (30); The second connecting arm (21) includes a second vertical plate and a third vertical plate arranged in parallel and intersecting. The bottom end of the second vertical plate is fixedly installed on the output shaft of the second joint (20), and the top end of the third vertical plate serves as the mounting seat of the third joint. The second vertical plate and the third vertical plate are connected by a second horizontal plate, which is set perpendicular to the second vertical plate.

4. The six degree-of-freedom desktop interactive robotic arm of claim 3, wherein, The third joint (30) and the fourth joint (40) are fixedly connected by a third connecting arm (31); The output shaft of the third joint (30) is perpendicular to the output shaft of the fourth joint (40); The third connecting arm (31) includes a fourth vertical plate and a fifth vertical plate that are vertically connected. The fourth vertical plate is fixedly mounted on the output shaft of the third joint (30), and one side of the fifth vertical plate serves as the mounting seat for the fourth joint (40).

5. A six degree-of-freedom desktop interactive robotic arm as claimed in claim 4, wherein, The fourth joint (40) and the fifth joint (50) are fixedly connected by the fourth connecting arm (41); The output shaft of the fourth joint (40) is perpendicular to the output shaft of the fifth joint (50); The fourth connecting arm (41) includes a sixth vertical plate and a seventh vertical plate that are vertically connected. The sixth vertical plate is fixedly mounted on the output shaft of the fourth joint (40), and one side of the seventh vertical plate serves as the mounting seat for the fifth joint (50).

6. A six degree of freedom table-top interactive robotic arm as claimed in claim 5, wherein, The fifth joint (50) and the sixth joint (60) are fixedly connected by the fifth connecting arm (51); The output shaft of the fifth joint (50) is perpendicular to the output shaft of the sixth joint (60), and the output shaft of the sixth joint (60) is coaxial with the output shaft of the fourth joint (40). The fifth connecting arm (51) includes an eighth vertical plate and a ninth vertical plate that are vertically connected. The eighth vertical plate is fixedly mounted on the output shaft of the fifth joint (50), and one side of the ninth vertical plate serves as the mounting seat for the sixth joint (60).

7. A six degree of freedom table-top interactive robotic arm as claimed in claim 6, wherein, The first connecting arm (11), the second connecting arm (21), the third connecting arm (31), the fourth connecting arm (41) and the fifth connecting arm (51) are all provided with wire grooves.

8. A six degree of freedom table-top interactive robotic arm as claimed in claim 7, wherein, A control box (70) is also connected to one side of the base. There is a wire hole between the control box (70) and the base. The control box (70) is used to install the control board.

9. A six degree of freedom table-top interactive robotic arm as claimed in claim 8, wherein, In the initial state, the installation heights of the first joint (10), the second joint (20), the third joint (30), and the fourth joint (40) are increased sequentially.

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